[doc30]

Essentially, the article says that fish, reptiles, amphibians and birds all evolved the capacity to see in the UV in the form of tetrachromic vision. Mammals were once that way, too. But during the time of the dinosaurs, mammals became nocturnal and lost two of the four receptors but gained better light sensitivity for nocturnal vision. Hence, all mammals are dichromatic. A certain lineage of primates experienced a mutation that shifted slightly one of the color receptors and evolved a weak version of trichromatic vision. Humans are part of that lineage. So, for those that say the eye could not have evolved because it is too complicated, be aware that it has now been shown that our eyes have de-evolved from non-mammilian vertebrates. They became much less 'complex' then genetic changes re-evolved some lost features. It sahows evolution works in both 'directions.'

One of my favorite examples from the article was about how birds of prey, kestrels in particular can see UV. Rodents leave urine-based scent trails, but urine has a 'UV color' that these birds can see. If you were a kestrel, you could see lines of urine trails zig-zagging across the coutryside and follow a trail to find your lunch. Also, birds without sexual dimorphism (i.e. you can't tell male from female visually) actually do have sexually dimorphic coloration in the UV. Other birds can see it but we can't.

[doc30]

ping

[Central Scrutiniser]

[RadioAstronomer]

Thanks for the post. Interesting read.

[Mike Darancette]

If you were a kestrel, you could see lines of urine trails zig-zagging across the coutryside and follow a trail to find your lunch.

I wonder if the nocturnal Owls have the ability to see in the UV?

[Billthedrill]

Five posts until some horse's patoot turns this article into an opportunity for another infantile crevo pissing contest. Counting down...

[djf]

There was a show about bird vision on Discovery a few years back.

At the very back of the retina, birds have this sort of "dimple" formation, packed with visual receptors.

The net result is that for the peripheral vision of birds, everything is seen as normal. But for a small circular section in the center of their field of vision, everything is magnified. So if they look straight at something, they "zoom in" on it.

[BaBaStooey]

Its such a shock that we are at the top of the food chain despite being "de-evolved."

[Mr. Mojo]

What Birds See

A Bald Eagle regularly sits atop a pine tree in my backyard about 150 feet from the water's edge (on the Puget Sound). Just stares at the water. ....hunting. His prety moves under the water, sometimes hundreds of feet offshore. I'm sittin' there with high-power binoculars unable to see a thing out there, but that great bird spots his prey every time, and swoops down out of the sky for the kill, emerging with fresh fish. Unfathomable vision.

[fella]

So, for those that say the eye could not have evolved because it is too complicated, be aware that it has now been shown that our eyes have de-evolved from non-mammilian vertebrates.

From this statement I can gather that a methodical and repeatable experiment has been performed?

[daybreakcoming]

Fascinating reading and thank you for posting it. It explains much about successful predatory of birds for example. I plan to tell my children about this as we have many hawks and owls around our home. As I write this, I realize the hawks have taken over the territory - have not seen/seen an owl around this year. Hmmmm...was it the hawks or Hurricane Rita as we didn't see/hear birds for quite some time after Rita.

[RobRoy]

What has been observed, according to the author: Different eyes, operating with different strengths.


What is pure conjecture in the article: that some sort of evolution is involved.

All the eyes could also have been designed that way.

There is proof for neither hypothesis, nor is either provable or disprovable. Dontcha just hate that?!

[GourmetDan]

The article assumes common descent and then explains differences in that context. In reality, eyes are merely different. The concept of descent w/ modification is imposed on the data, not an artifact of the data itself.

Statements like 'Mammals were once that way too', 'Mammals became nocturnal and lost two receptors' are unsupportable and are mere conjecture.

Makes a nice story and that's all that counts to evos.

How good is your imagination?

[Mogollon]

A certain lineage of primates experienced a mutation that shifted slightly one of the color receptors and evolved a weak version of trichromatic vision. Humans are part of that lineage.

What was the mechanism for this miraculous mutation that effected all subsequent primates? What was the mutagenic agent that caused this specific mutation? Care to speculate?

[mikrofon]

So much for the concept of "bird's-eye view"...

[js1138]

Getting back to the topic of the thread, I find the topic of color vision rather interesting. I have a number of color blind members of my family, including a nephew with total color blindness -- no color receptors at all.

Of course this means he has great difficult with fine detail and requires large print books. As an infant he was thought to be blind.

As a tradeoff, he has phenomenal night vision.

[newguy357]

So, for those that say the eye could not have evolved because it is too complicated, be aware that it has now been shown that our eyes have de-evolved from non-mammilian vertebrates.

Huh? I don't follow your progression in this sentence. If someone doesn't believe the eye evolved, what does the second part of your sentence do to convince him otherwise?

[microgood]

Rodents leave urine-based scent trails, but urine has a 'UV color' that these birds can see. If you were a kestrel, you could see lines of urine trails zig-zagging across the coutryside and follow a trail to find your lunch.

Thanks for that explanation. That is really cool. Seems kind of unfair, though.

[D-fendr]

We humans customarily assume that our visual system sits atop a pinnacle of evolutionary success.

Not this human. Tis our brains and consciousness that sit atop a pinnacle, not our physical capabilities. I thought pretty much every adult knew our eyes aren't the best - neither is our sense of smell or hearing.

[Tall_Texan]

As a parrot owner, this was interesting reading. I have read that parrots accept or reject food based on some UV coloring. It explains why they are such messy eaters because they will eat, say, only the freshest parts of a fruit and discard the rest of it. We humans look at that and see messiness and wastefulness. The bird, however, sees it like we would if we were trimming fat off a steak. mmmm...steak....

[freedumb2003]

What Birds See

Human eye:

Birds' Eye